Framed pleated air filter with upstream bridging filaments

ABSTRACT

A framed pleated air filter, including a non-self-supporting, compressible, pleated air filter media with a plurality of oppositely-facing pleats and with a plurality of upstream pleat tips and downstream pleat tips, the pleated air filter media further including a plurality of bridging filaments that are bonded to at least some of the upstream pleat tips. The framed pleated air filter does not include any support member on the downstream face of the pleated air filter media.

BACKGROUND

Framed, pleated filters are commonly used in air filtrationapplications. In such filters, support is often provided with support onthe downstream side of the pleated filter media.

SUMMARY

Herein is disclosed a framed pleated air filter, including anon-self-supporting, compressible, pleated air filter media with aplurality of oppositely-facing pleats and with a plurality of upstreampleat tips and downstream pleat tips, the pleated air filter mediafurther including a plurality of bridging filaments that are bonded toat least some of the upstream pleat tips. The framed pleated air filterdoes not comprise any support member on the downstream face of thepleated air filter media. These and other aspects of the invention willbe apparent from the detailed description below. In no event, however,should this broad summary be construed to limit the claimable subjectmatter, whether such subject matter is presented in claims in theapplication as initially filed or in claims that are amended orotherwise presented in prosecution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary framed pleated air filterviewed from the downstream side.

FIG. 2 is a perspective view of an exemplary pleated air filter with thesupport frame omitted, viewed from the upstream side.

FIG. 3 is a side schematic cross sectional view of a portion of theframed pleated air filter of FIG. 1, taken along line 3-3 of FIG. 1.

FIG. 4 is a side schematic cross sectional view of portions of a nestedstack of exemplary nestable framed pleated air filters.

Like reference symbols in the various figures indicate like elements.Unless otherwise indicated, all figures and drawings in this documentare not to scale and are chosen for the purpose of illustratingdifferent embodiments of the invention. In particular the dimensions ofthe various components are depicted in illustrative terms only, and norelationship between the dimensions of the various components should beinferred from the drawings, unless so indicated.

DEFINITIONS

Although terms such as “top”, “bottom”, “upper”, “lower”, “under”,“over”, “front”, “back”, “up” and “down”, and “first” and “second” maybe used in this disclosure, it should be understood that those terms areused in their relative sense only unless otherwise noted. As used hereinas a modifier to a property, attribute or relationship, the term“generally”, unless otherwise specifically defined, means that theproperty, attribute or relationship would be readily recognizable by aperson of ordinary skill but without requiring absolute precision or aperfect match (e.g., within +/−20% for quantifiable properties); theterm “substantially” means to a high degree of approximation (e.g.,within +/−10% for quantifiable properties) but again without requiringabsolute precision or a perfect match. Terms such as “outer”, “outward”,“outwardmost”, “outwardly”, and the like, mean in a direction generallyaway from the geometric center of the framed air filter. Terms such as“inner”, “inward”, “inwardmost”, “inwardly”, and the like, mean in adirection generally toward the geometric center of the framed air filtermedia. The term “upstream” is used to denote the side of an air filterfrom which moving air (in an HVAC system) impinges on the filter media.The upstream side corresponds to the lower side of framed filter 1 asshown in FIG. 1 and to the upper side of pleated filter media 10 asshown in FIG. 2. The term “downstream” is used to denote the side of anair filter through which air exits the filter media, corresponding tothe upper side of framed filter 1 as shown in FIG. 1 and to the lowerside of pleated filter media 1 as shown in FIG. 2. (FIG. 3 is markedwith “u” and “d” axes to aid in recognition of upstream and downstreamsides of the framed filter and components thereof.)

The term “non-self-supporting” denotes a pleated air filter media thatis not capable, in the absence of a support frame that is mounted to themajor edges of the pleated filter media to form a framed air filter, ofwithstanding the forces encountered due to forced-air flow in a typicalresidential HVAC system, as discussed in detail later herein. Suchnon-self-supporting pleated air filter media by definition does notencompass pleated air filter media (such as those described e.g. in U.S.Pat. Nos. 8,231,700, 7,896,940 and 6,521,011, all to Sundet, and U.S.Patent Application Publication 2013/0101477 to Both) for which the useof a frame is described as optional.

The term “nestable” denotes framed filters that are configured so thattwo or more such filters (of like shape, size, and thickness) can bestacked together, without significantly deforming the frames of thefilters, at a nesting spacing that is less than 85% of the thickness ofeach filter, as discussed in detail herein.

The term “compressible” with reference to a pleated filter mediumdenotes that the pleats of the filter medium can reversibly compresswhen moderate force is applied to the pleats (e.g., when the framed airfilter is nested with other framed air filters of like size and shape),and that the pleats can spring back to their original pleatedconfiguration when the force is removed (e.g., when the filter isremoved from a nested condition).

DETAILED DESCRIPTION

Shown in FIG. 1 in perspective view from the downstream side is anexemplary framed air filter 1. Shown in FIG. 3 is a cross-sectionalslice view of a portion of the exemplary air filter of FIG. 1, takenalong line 3-3 of FIG. 1. Framed air filter 1 comprises an upstream side2 and a downstream side 3. Air filter 1 comprises pleated filter media10 and support frame 12 mounted generally on, and surrounding, theperimeter of pleated filter media 10. Framed air filter 1 may often berectangular in shape (which specifically includes square shapes) withcorners 4, with pleated filter media 10 thus having a generallyrectangular perimeter (which does not preclude irregularities, notches,chamfered or angled corners, or the like, in the perimeter of filtermedia 10). Framed filters of this type are distinguished from e.g.cylindrical (cartridge) filters.

In FIG. 1, framed air filter 1 is viewed from the downstream side. (Suchfilters are often marked by the manufacturer to identify the upstreamand downstream sides, in order that the filter be installed in theproper orientation in an HVAC system.) In framed air filters of thisgeneral type (i.e., with “pinch” frames as described in further detailherein), the downstream side of a framed air filter may be an“open-ended” side comprising outwardly flared edges of frame 12, as seene.g. in FIG. 1 and in further detail in FIG. 3. That is, such filtersare often placed into forced air ventilation systems with the closed-endside of the filter facing the stream of incoming air (i.e., facingupstream) and with the open-ended side of the filter facing downstream(e.g. with the terminal ends 145 of at least some of the frame sidewallsresting against support flanges of the forced air ventilation system).

Pleated filter media 10 comprises an upstream face 25 and a downstreamface 35. As shown in further detail in FIG. 2, which shows an exemplarypleated filter media 10 with frame 12 omitted, pleated filter media 10comprises a plurality of upstream pleats 20, oriented in generallyparallel relation to each other. Each upstream pleat 20 comprises anupstream pleat tip 21 and each adjacent pair of upstream pleats 20defines an upstream pleat valley 22 therebetween. Flowing air may passinto upstream valley 22 and into upstream pleat walls 23 so as topenetrate into pleated filter media 10. Pleated filter media 10 furthercomprises a plurality of downstream pleats 30, in generally parallelrelation to each other and in oppositely-facing configuration fromupstream pleats 20. Each downstream pleat 30 comprises a downstreampleat tip 31 and each adjacent pair of downstream pleats 30 defines adownstream pleat valley 32 therebetween. Flowing air may pass out ofdownstream pleat walls 33 so as to exit pleated filter media 10.

Bridging Filaments

Framed air filter 1 comprises a plurality of bridging filaments 40 onupstream face 25 of pleated filter media 10. At least portions of atleast some of the bridging filaments 40 are bonded to at least portionsof at least some of the upstream pleat tips 21 of pleated filter media10 and can help locally stabilize pleated filter media 10 as disclosedherein.

By definition, a bridging filament is not pleated along with pleatedfilter media 10. Also by definition, a bridging filament is one thatextends between, and is bonded to, at least two upstream pleat tips 21of pleated filter media 10; or, that is bonded to and/or entangled withother filaments so that the filaments collectively bridge the distancebetween at least two upstream pleat tips 21 of pleated filter media 10(with at least some of the filament portions that are in contact withthe upstream pleat tips being bonded to the pleat tips). That is, insome exemplary embodiments bridging filaments might be collectivelysupplied by e.g. filaments of a spun-bonded web (scrim), whichfilaments, even if they are too short and/or are oriented so that theydo not extend between upstream pleat tips, are bonded to other filamentsso as to collectively bridge the distance between the upstream pleattips (with the filament portions that are in contact with the upstreampleat tips being bonded thereto). In other exemplary embodimentsbridging filaments might be collectively supplied by e.g. filaments ofan expanded metal (such as e.g. the products available from WallnerTooling/Expac, Rancho Cucamonga, Calif.), even though individualsegments of the metal filaments (between junction points with otherindividual segments) may (or may not) be long enough to extend betweentwo upstream pleat tips.

In at least some embodiments, however, bridging filaments 40 willcomprise an average length that is at least 100%, 200%, 400%, or 800% ofthe spacing between consecutive upstream pleat tips 21, and/or will bearranged so that at least some individual filaments extend between, andare bonded to, at least two upstream pleat tips 21 of pleated filtermedia 10.

Not being pleated, bridging filaments 40 will often comprise a generallyplanar configuration (as shown in exemplary embodiment in FIG. 2). Thismay be characterized herein as filaments 40 collectively forming astabilizing plane, noting that the term is used for convenience and thatthe filaments do not have to form a perfectly flat plane (e.g., someslight sagging of portions of filaments 40 into upstream pleat valleys22 may occur). Regardless of how closely the filaments approach a trueplane, most portions of most filaments 40 are spaced away from themajority of the area of upstream pleat walls 23; that is, they arespaced apart from all such pleat wall areas except those at, or veryclose to, upstream pleat tips 21. Bridging filaments 40 are thus bydefinition in discontinuous contact with the upstream face 25 of pleatedfilter media 10.

Bridging filaments may be provided on the upstream face of pleatedfilter media 10 in any suitable manner and in any suitable arrangement.An exemplary arrangement of a plurality of bridging filaments 40 isshown in FIG. 2, which is a view from the upstream side of pleatedfilter media 10 (that is, with pleated filter media 10 inverted from theconfiguration shown in FIG. 1). In embodiments of the general type shownin FIG. 2, at least some bridging filaments 40 may be oriented at leastgenerally perpendicular to (e.g., within +/− about 5 degrees of 90degrees to) the pleat direction of pleated filter media 10 (with pleatdirection meaning a direction parallel to pleat tips 21 and 31, assignified by the arrow in FIG. 2). In such cases, a bridging filamentmay extend between, and be bonded to, e.g. three, four, eight, or moreupstream pleat tips 21. In some embodiments, at least some bridgingfilaments may be continuous, meaning that they extend along the entirelength of pleated filter media 10 (as in the exemplary design of FIG.2). Such continuous bridging filaments thus will not be severed orotherwise made discontinuous anywhere along the entire length of pleatedfilter media 10. In any case, a bridging filament 40 (continuous or not)will be distinguished from filaments that are cut or otherwise made soshort that they do not extend between at least two upstream pleat tips(and are not bonded to other filaments in such manner to collectivelyform bridging filaments, as discussed above). In some embodimentsbridging filaments 40 are at least generally straight, as shown inexemplary embodiment in FIG. 2. In embodiments of this type, at leastsome of the bridging filaments 40 may be at least generally parallel toeach other, again as shown in exemplary illustration in FIG. 2. However,other arrangements are possible, as discussed later herein.

Bridging filaments 40 can advantageously locally stabilize pleatedfilter media 10 to minimize any local deformation of a pleat due to thepressure of an airstream impinging on upstream face 25 of pleated filtermedia 10. Specifically, filaments 40 as provided on the upstream face 25of pleated filter media 10 can the minimize local deformation of atleast upstream pleats 20, in a way that may not be possible werefilaments 40 to be provided only on the downstream face 35 of pleatedfilter media 10. If filaments 40 (or, in general, any other type ofsupport) were to be provided on the downstream face of pleated filtermedia 10, the pressure of the impinging air could cause upstream pleats20 to locally deform, e.g. collapse, toward the downstream side of thepleated filter media, a process that filaments 40 could do little ornothing to prevent. In contrast, with filaments 40 placed on theupstream face of the pleated filter media and bonded to the upstreampleat tips, the filaments may largely prevent the upstream pleats fromlocally collapsing or deforming toward the downstream side of thepleated filter media under the air pressure. Moreover, since thepressure of the moving air will tend to “inflate” the downstream pleats,the filaments, being bonded to the upstream pleat tips, may also locallystabilize the downstream pleats, e.g. by limiting the inflation of thedownstream pleats so as to e.g. prevent any unacceptable billowing orballooning of the downstream pleats. It will thus be appreciated thatbridging filaments 40 can act to locally stabilize pleated filter media10, without causing pleated media 10 to be self-supporting (and withoutcompromising the ability of framed air filters 1 to be optionally nestedif this is desired).

Any suitable filaments 40 may be used, made of any suitable materials.In some embodiments, filaments 40 may be non-elastic. Non-elastic asdefined herein encompasses any material that does not have therelatively high reversible extensibility (characterized e.g. by theability to be reversibly elongated to e.g. 100% or more withoutundergoing plastic deformation) characteristic of elastic materials suchas natural rubber, SBR rubber, lycra, etc. Thus, common polymericmaterials, e.g. extrudable materials (including but not limited to e.g.polypropylene, poly(lactic acid), polyethylene terephthalate and thelike), may be used to form filaments 40. In other embodiments, filaments40 may be made of an elastic material. Regardless of the specificcomposition of filaments 40, it may be desired that in at least someembodiments, filaments 40 may not extend or elongate to any significantextent (e.g., more than about 10%) under the forces present upon theexposure of framed air filter 1 to a typical residential HVAC airstream.In some embodiments, filaments 40 as disclosed herein are flexible,meaning that filaments 40 can (individually and collectively) be easilyand reversibly bent, curved, rolled up etc. In specific embodiments,bridging filaments 40 are not comprised of a shape-memory polymer.

In various embodiments, filaments 40 may comprise an average diameter(or equivalent diameter in the case of filaments with a non-circular orirregular cross-section) of at most about 2, 1, 0.5, 0.2, or 0.1 mm. Infurther embodiments, filaments 40 may comprise an average diameter orequivalent diameter of at least about 0.05, 0.10, or 0.20 mm. Filaments40 may comprise any suitable shape when viewed in cross section, (e.g.,generally round, square, oblong, etc.). Filaments 40 can comprisesuitable spacings between individual filaments as desired (e.g., whenfilaments 40 are arranged e.g. in parallel to each other so that such anaverage spacing can be measured). In various embodiments, the filamentspacing can be at least about 2 mm, at least about 4 mm, or at leastabout 6 mm. In additional embodiments, the filament spacing can be atmost about 20 mm, at most about 15 mm, at most about 10 mm, or at mostabout 8 mm. The filament spacings can be relatively constant or can bevaried. Some inherent variation in filament spacing may occur inproduction and handling of filaments, of course. Regardless of thespecific arrangements, a suitable set of filaments 40 will collectivelycomprise a highly open structure (in various embodiments, comprisinggreater than at least 80, 90, or 95% open area) so as to allowsufficient airflow into pleated filter media 10.

Filaments 40 may be made of any material, provided in any form and inany manner, as long as the material, in combination with the dimensions(e.g., width, thickness) of the filaments, provides the desiredcombination of physical properties (e.g., flexibility andinextensibility). Such materials may include organic polymeric materials(whether naturally occurring or synthetic, including those alreadymentioned above), inorganic materials (e.g., fiberglass), metals (suchas metal meshes, e.g. expanded metals) and so on. In some embodiments,filaments 40 are not made of metal or of inorganic materials such asfiberglass.

As discussed above, in some embodiments, filaments 40 may be individualfilaments that are individually provided (e.g., polymeric filaments thatare extruded onto the upstream pleat tips 21 of pleated filter media 10as described later herein). In other embodiments, filaments 40 may beprovided as filaments of a scrim. In this context, the term scrim isused to broadly encompass any collection of filaments that are incontact with each other, achieved by any method of manufacture.Specifically, the term scrim is not limited to organic polymericmaterials but rather includes metal meshes or netting (e.g. expandedmetals as mentioned earlier herein), inorganic scrims made of e.g.fiberglass, and so on. In some embodiments, such a scrim may be apre-existing scrim, meaning a scrim that has been pre-made and that hassufficient mechanical integrity to be handled, and brought into contactwith the upstream pleat tips, as a unit.

In some embodiments, such a scrim (whether pre-existing or not) maycomprise at least some bridging filaments 40 that are oriented generallyperpendicular to the pleat direction and that are parallel to each other(e.g., that are oriented in similar manner to the filaments 40 of FIG.2), with other filaments also present (that may or may not be bridgingfilaments) and which other filaments may be oriented in variousdirections. In some embodiments of this general type a collection ofbridging filaments 40 may be provided in the form of plastic mesh ornetting, a knit or woven fabric, and so on (noting however that any suchmaterial does not necessarily have to be bonded to the pleated filtermedia so that a set of filaments of the material is strictly, or evengenerally, perpendicular to the pleat direction.)

In some embodiments, rather than filaments being present that areoriented at least generally perpendicular to the pleat direction,filaments may be present at a wide variety of orientations (andspacings). Such filaments may follow curves, loops, tortuous paths, andso on, as long as a sufficient number of filaments bridge the gapsbetween upstream pleat tips 21 to serve as bridging filaments. That is,filaments 40 may be provided as part of a scrim that comprises acollection of randomly-oriented filaments, as long as such filaments aresufficiently long and are bonded and/or entangled with each other toserve as bridging filaments as defined herein. Such a scrim might bee.g. a spun-bonded web, spun-laced web, a carded web, a Rando web, alaminate of multiple webs, and so on.

It is thus emphasized that bridging filaments 40 may be provided in awide variety of ways. However, in some particular embodiments asdiscussed above, bridging filaments 40 are provided only in the form offilaments that are oriented at least generally parallel to each otherand that are not connected with each other by any other filaments. Suchembodiments preclude the use of filaments that are part of e.g. apre-existing scrim that includes filaments oriented in a wide variety ofdirections; e.g. scrims with multi-directional fibers such astri-directional scrims and the like. Regardless of the specific natureof the bridging filaments on the upstream face of the pleated filtermedia, no bridging filaments of any kind will be present on thedownstream face of the pleated filter media. In fact, no support memberof any kind will be present on the downstream face of the pleated filtermedia, as discussed in detail later herein.

Filter Media

Pleated filter media 10 may be any suitable media that is pleatable andthat is capable of air filtration. Potentially suitable materials mayinclude e.g. paper; porous films of thermoplastic or thermosetmaterials; nonwoven, such as melt blown or spunbond, webs of syntheticor natural fibers; scrims; woven or knitted materials; foams; electretor electrostatically charged materials; fiberglass media; or laminatesor composites of two or more materials. A nonwoven polymeric webcomprised of polyethylene, polypropylene or poly(lactic acid) may besuitable, for example. Any suitable method of making a nonwoven web(e.g., melt-blowing, melt-spinning, carding, and so on) may be used.Filter media 10 may also include sorbents, catalysts, and/or activatedcarbon (granules, fibers, fabric, and molded shapes).

Laminated media can also be used as filter media 10. Such media mayconsist of laminated layers of the media discussed above or of othersubstrates laminated to one or more layers of filter media, for example.In some embodiments, a prefilter layer may be used on the upstream sideof filter media 10. Such a prefilter layer may comprise e.g.polypropylene, polyethylene, polyethylene terephthalate, poly(lacticacid), or blends of these materials. In other words, in some embodimentspleated filter media 10 may comprise a base (e.g., filtration) layer,along with any other layer or layers as desired for any purpose, as longas it allows pleated media 10 to remain non-self-supporting as definedand described herein. For example, a highly open plastic netting or meshmight be laminated to the pleated media, in order to e.g. enhance theabrasion resistance of the media. Any such layer may be bonded to e.g. abase (e.g. filtration) layer by any suitable method, e.g. bymelt-bonding, by way of an adhesive (hot melt adhesive,pressure-sensitive adhesive, and so on).

In specific embodiments, electret filter webs can be formed of splitfibrillated charged fibers e.g. as described in U.S. Pat. No. RE 30,782.Such charged fibers can be formed into a nonwoven web by conventionalmeans and optionally joined to a scrim such as disclosed in U.S. Pat.No. 5,230,800 forming an outer support layer. In other specificembodiments, filter media 10 can be a melt blown microfiber nonwovenweb, e.g. such as disclosed in U.S. Pat. No. 4,813,948, which canoptionally be joined to a secondary layer during web formation asdisclosed in that patent, or subsequently joined to a secondary web inany conventional manner.

Filtration media that may be particularly suitable for certainapplications might include e.g. media of the general type described inU.S. Pat. No. 8,162,153 to Fox; media of the general type described inU.S. Patent Application Publication 2008/0038976 to Berrigan; and, mediaof the general type described in U.S. Patent Application Publication2004/0011204 to Both.

Pleated filter media 10 may comprise any suitable pleat frequency. Invarious embodiments the pleat frequency may be at most about 1.6, 1.2,1.0, or 0.8 pleats per cm; in further embodiments the pleat frequencymay be at least about 0.3, 0.4, or 0.5 pleats per cm. (In this contextthe pleat frequency means the number of times that a reference point,e.g. an upstream pleat tip, repeats per cm of distance). In variousembodiments, the pleat height (pleat amplitude) of media 10 (defined asthe distance in an upstream-downstream direction (i.e., a directionorthogonal to the overall major plane of filter 1/filter media 10), fromthe upstream surface of an upstream pleat tip to the downstream surfaceof a downstream pleat tip), can be at least about 2, 4, 6 or 8 mm. Infurther embodiments, the pleat height may be at most about 12, 6, 4, 2,or 1 cm. In some embodiments the pleats of pleated media 10 may besinusoidal, meaning that the tips of such pleats have an average radiusof curvature of at least about 2 mm. In various embodiments, suchsinusoidal pleats may comprise tips with an average radius of curvatureof at least about 3, 4, 5, or 6 mm. Sinusoidal pleats as disclosedherein (and as shown in exemplary embodiment in FIGS. 3 and 4) aredistinguished from e.g. “zig-zag” style pleats that comprise extremelyflat walls that meet at pleat tips with extremely small radii ofcurvature. (Such zig-zag style pleats are often used in e.g.self-supporting filter media and are often achieved e.g. by scoring thefilter media to provide a score line, along which the media is thenfolded to form a very sharp pleat.)

Non-Self-Supporting Pleated Filter Media

As discussed earlier herein, pleated filter media 10 isnon-self-supporting, even in the presence of bridging filaments 40 onthe upstream face thereof. That is, even though bridging filaments 40may help to stabilize the pleats of pleated filter media 10 againstlocal deformation as disclosed earlier herein, the presence of bridgingfilaments 40 is not sufficient to render pleated filter media 10self-supporting. By non-self-supporting is meant a pleated air filtermedia that is not capable, in the absence of a support frame that ismounted to the major edges of the pleated filter media to form a framedair filter, of withstanding the forces encountered due to forced-airflow in a typical residential HVAC system. Specifically,non-self-supporting denotes a pleated air filter media that, when placedin a conventional holding fixture of a residential HVAC system without asupporting edge frame, is unable to withstand the forces developed whenair impinges the upstream face of the air filter media so as to developa pressure of at least 0.10 kPA (0.4 inch of water). (By unable towithstand such forces means that the pleated air filter media collapses,deforms, becomes dislodged, ruptures, or the like, so as to render theperformance of the air filter media unsatisfactory.)

Methods of Making

Filter media 10 can be pleated by any suitable method by which pleatsmay be formed in a media prior to bridging filaments 40 being bonded toupstream pleat tips thereof (noting that the term pleated filter mediaas used herein does not encompass filter media that is formed into afolded or puckered shape by way of the e.g. shrinking of a shape-memorypolymer that is attached to portions thereof). Particularly advantageousmethods might include the processing of the media through a set ofcorrugating gears, e.g. in any suitable variation of the methodsdisclosed in e.g. U.S. Pat. No. 5,256,231. Bridging filaments 40 may bebonded to upstream pleat tips of a pleated filter media 10 by anysuitable method. If the filaments are provided as a pre-existing scrim,such a scrim can be applied to the upstream face of pleated filter media10, and bonded to at least some of the upstream pleat tips thereof, byany suitable method. For example, a scrim may be obtained e.g. as acontinuous roll, a bonding adhesive can be applied thereto (e.g., bycoating the adhesive onto at least some surfaces of filaments of thescrim), and the scrim then contacted with the pleated media so as tocause bonding between adhesive-coated portions of the filament andportions of the upstream pleat tips that they are contacted with.

Other bonding methods (e.g., ultrasonic bonding, melt-bonding (includinge.g. heat-sealing), and so on), are also possible. In embodiments inwhich filaments 40 are not provided as part of a pre-existing scrim,they may be conveniently melt-extruded onto the upstream pleat tips of apleated filter media, e.g. while the media is still resident on acorrugating (pleating) gear or any other kind of corrugating apparatus.Such methods could be any suitable variation of the methods disclosed ine.g. U.S. Pat. Nos. 5,256,231; 5,620,545; and 7,052,565, all of whichare incorporated by reference herein in their entirety. In embodimentsin which filaments 40 are melt-bonded to the upstream pleat tips ofmedia 10, the composition of filaments 40 and the fibers of media 10(specifically, the outermost fibers of media 10, if media 10 comprisesmultiple layers) may be advantageously chosen to facilitate suchmelt-bonding. For example, the filaments and fibers may be made ofmaterials that are sufficiently compatible to allow melt-bonding tooccur. In specific embodiments, filaments 40 and the fibers of media 10may be comprised of the same type of polymer (e.g., they may both bepolypropylene; they may both be poly (lactic acid), etc.). It will benoted that in some circumstances (e.g., when the filaments 40 aremelt-extruded onto the pleat tips) some penetration of the moltenfilament material into the spaces between the fibers of media 10 mayoccur, which may augment the bonding process by achieving at least somephysical entanglement or entrapment.

However provided, in at least some embodiments filaments 40 may beprovided (in a spaced-apart manner) generally across the entire width(that is, the dimension that is generally orthogonal to the pleatdirection and to the upstream-downstream axis of the filter media) ofthe pleated filter media. Pleated filter media 10 may be trimmed or cutto the desired final width before or after the bonding of the filamentsthereto, as desired.

The pleat direction of filter media 10 relative to frame 12 (and thus tothe finished filter 1) and the orientation (i.e., of the long axes) offilaments 40 relative to frame 12, may each be chosen as desired. Insome embodiments in which filter 1 is non-square, the pleat directionmay oriented generally perpendicular to the long axis of filter 1 (as inthe design of FIG. 1); and, filaments 40 may be oriented generally inalignment with the long axis of filter 1 (as in the design of FIG. 2,although the frame is omitted from the Figure). In some embodiments theterminal ends of filaments 40 may generally coincide with terminal edgesof pleated filter media 10, as shown in FIG. 2 (however, the filaments40 do not necessarily have to be straight and/or parallel, as discussedabove). In other embodiments, the terminal ends of at least somefilaments 40 may extend beyond a terminal edge of pleated media 10(although such ends might end up folded back onto a border portion ofpleated media 10 when a frame is applied to the edges of the pleatedmedia).

Frame

A frame (i.e., a support frame) 12 is applied to the perimeter ofpleated filter media 10 (comprising filaments 40 bonded to upstreampleat tips thereof) to form framed pleated air filter 1. Pleated filtermedia 10 being non-self-supporting (even in the presence of filaments40) as defined earlier herein, frame 12 is required in order for pleatedfilter media 10 to be properly supported in place in a residential HVACsystem. Frame 12 may conveniently take the form of a rectangular framewith four major elongate frame portions that are each mounted on one ofthe four major edges of the filter media. For convenience in describingsuch generally rectangular geometry, the four major portions of frame 12may occasionally be referred to herein by a lettered subscript (e.g., a,b, c, or d). It will be recognized that in a rectangular filter,opposing frame portions (e.g., portions 12 a and 12 c; and, portions 12b and 12 d, as shown in FIG. 1) may in some cases be identical to eachother. In the case of a square filter, all four portions may in somecases be identical to each other. As pictured in FIG. 1, frame portions12 b and 12 d are portions that are aligned parallel to the pleatdirection of pleated media 10; frame portions 12 a and 12 c are portionsthat are aligned orthogonal to the pleat direction. Any two neighboringframe portions of frame 12 meet to form a corner 4 of frame 12. It isemphasized that major frame portions 12 a, 12 b, etc., do notnecessarily correspond to individual frame pieces from which frame 12 isassembled. In fact, frame 12 might be made from e.g. a single framepiece, or e.g. from two, three, or four frame pieces that are assembledtogether and connected to each other to form the finished frame 12.

In many embodiments, support frame 12 may be a “pinch” frame as shown inexemplary embodiment in FIGS. 1 and 3. As shown in exemplary embodimentin FIG. 3, a pinch frame is defined by the presence (on at least onemajor portion of frame 12), of a downstream flange 160 and an upstreamflange 130, which flanges comprise at least inward terminal ends thatare “pinched” toward each other (so that they are spaced apart from eachother a distance that is much less than (e.g., is less than 15% of) theoverall thickness of the frame). Such flanges may capture (e.g., pinch)border portion (perimeter edges) 7 of filter media 10 therebetween. Apinch frame is thus distinguished from e.g. a U-shaped (channel) framethat has upstream and downstream flanges that are spaced apart from eachother a distance that is very similar to (e.g., is within 20% of) theoverall thickness of the frame.

It will be appreciated that some asymmetry will be present in framedfilter 1 owing to the pleating of filter media 10. Specifically, withreference to FIGS. 1-3, the upstream and downstream flanges of majorframe portions 12 b and 12 d, which flanges/portions will be alignedwith the pleat direction, may capture a border portion 7 of pleatedfilter media therebetween, without necessarily having to significantlydeform any portion of any pleats (as evidenced by inspection of FIG. 3).In contrast, the upstream and downstream flanges of major frame portions12 a and 12 c, which flanges/portions will be oriented perpendicular tothe pleat direction, may deform (i.e., flatten) pleated portionstherebetween in the action of being pinched together. This may be of noconsequence as long as the pleat portions can be flattened sufficientlyto prevent any air leakage between border portion 7 and the varioussurfaces of the frame sidewalls and flanges. It will be appreciated thatin at least some embodiments, compressibility of the pleated filtermedia 10 (as described later herein) may help ensure that pleats can besufficiently flattened between the frame flanges that no such leakagepathways exist.

In many cases, most or all of the area of frame flanges 130 and 160 (notjust inward terminal ends thereof) may be pinched together; often, mostor all portions of flanges 130 and 160 will be at least generallyparallel to each other (as shown e.g. in FIG. 3). In any case, at leastthe inward terminal ends of flanges 130 and 160 will define a pinchplane (P_(i)) as indicated in FIG. 3, meaning the plane in whichperimeter edges 7 of filter media 10 are captured by the flanges (often,the perimeter edges of filter media 10 are bonded to one or bothflanges, e.g. by adhesive bonding over a wide area or adhesivepoint-bonding, by stapling, or by any combination of these methods).

In some embodiments each major portion of frame 12 may comprise an outersidewall 140, which extends outward and downstream from flange 130 andis foldably connected thereto by fold line 135; and, inner sidewall 150,which extends outward and downstream from flange 160 and is foldablyconnected thereto by fold line 155, with outer sidewall 140 and innersidewall 150 being foldably connected by fold line 145. (In manyembodiments, fold line 145 may provide a terminal downstream end/edge offrame 12.) Thus, in some embodiments a major portion of frame 12 may beconveniently formed by the folding of a suitable precursor material(e.g., paperboard) along fold lines so as to provide flanges 130 and 160and sidewalls 140 and 150. However, any suitable frame construction maybe used; i.e. any major portion of frame 12 may be made of any suitablematerial (whether paperboard, plastic etc.) and may be formed e.g. byfolding of a single frame piece, by the assembling of multiple pieces toeach other, and so on. In many embodiments, all four major frameportions may each comprise upstream and downstream flanges and inner andouter sidewalls and foldable connections therebetween.

As used herein, the term foldable signifies that the frame portion isformed (i.e., into the general configuration shown in FIGS. 1 and 3) byfolding the various flanges and sidewalls of the frame portion relativeto each other along the various fold lines. The term does not denotethat the finished frame portion (or the entirety of finished frame 12),once formed, is foldable in the sense that it can be collapsed or foldedflat. In fact, in various embodiments frame 12, once formed, is not becollapsible or foldable; thus, the herein-described (optional) nestingof multiple framed filters can be achieved without necessitating (orinvolving) any significant deformation of the frames of the nestedfilters.

Details of particular support frames that may be suitable for the usesdisclosed herein are provided in U.S. patent application Ser. No.13/490,545, filed 7 Jun. 2012 and entitled Framed Air Filter with OffsetSlot, and Method of Making, which is incorporated herein by reference inits entirety. The finished (framed) filter may be of any suitable sizefor any desired application.

Each major portion of a frame 12 (e.g., portions 12 a-12 d as shown inFIG. 1) will comprise a sidewall. In some embodiments, such a sidewallmay be comprised of an inner sidewall 150 and an outer sidewall 140 asshown in exemplary embodiment in FIGS. 3 and 4. In some embodiments,inner sidewall 150 and outer sidewall 140 may be positioned at an angleto each other (when viewed in cross section as shown in FIG. 3, and asmeasured from the vertex provided by fold line 145) of less than about40, 30, 20, or 10 degrees. In such embodiments, at least portions ofinner sidewall 150 and outer sidewall 140 may be generally parallel toeach other and may closely approach each other (as shown in FIG. 3). Insuch embodiments, areas of inner sidewall 150 and outer sidewall 140 maybe bonded, e.g. adhesively bonded, to each other, e.g. if desired toenhance the strength of frame 12. In other embodiments, particularly inwhich an angle of e.g. at least about 20, 40 or more degrees is providedbetween outer and inner sidewalls 140 and 150, a gap (e.g., in the rangeof 0.1-2 mm, and which may be filled with e.g. air or at least partiallyfilled with adhesive) may exist between portions of the outer and innersidewalls. Arrangements of this general type are depicted in exemplaryembodiment in FIG. 4.

The sidewalls of major portions of frame 12 can have any suitable angle.As a convenient reference, the angle established by outer sidewall 140(as seen most easily in FIG. 3) will be used to characterize such asidewall angle. Specifically, a sidewall angle is the angle betweenouter sidewall 140 and the major plane of framed filter 1/pleated media10 (such a sidewall angle can also be considered to be the angle betweenthe outer sidewall and the upstream-downstream axis of the filter, plus90 degrees). An angle of 90 indicates a “vertical” sidewall that isaligned with upstream-downstream (airflow) direction defined by theoverall major plane of the filter (e.g., a sidewall of the angletypically found in conventional U-shaped channel frames). An angle ofless than 90 indicates an inwardly-angled sidewall.

In some embodiments, each major portion of frame 12 may comprise asidewall angle ranging from e.g. about 60 degrees to 100 degrees. Inparticular embodiments, such a sidewall angle may be about 90 degrees.In some embodiments, each major portion of frame 12 may optionallycomprise an outwardly angled outer sidewall to facilitate optionalnesting of the framed filters. That is, a sidewall angle of e.g. atleast about 100, 110, 120, or 130 degrees, and of at most about 160,150, or 140 degrees, will facilitate the nesting of framed filters asdisclosed herein. (By way of specific example, the sidewall angle offrame portion 12 b as shown in FIG. 3, is about 130 degrees). Often,each major portion of frame 12 may comprise a sidewall angle that isgenerally, or substantially equal, to the sidewall angle of the othermajor portions of frame 12. However, some asymmetry may be allowed.

Optional Nestability

The disclosures herein allow the optional production of framed filtersthat are nestable. The term “nestable” denotes framed filters that areconfigured such that two or more such filters (of like shape, size, andthickness) can be stacked together, without significantly deforming theframes of the filters, at a nesting spacing that is less than 85% of thethickness of each filter. This ratio of nesting spacing to filterthickness (as a percentage) can be referred to as a nesting factor. Forpurposes of such calculations, the thickness of a framed filter “t” isthe distance (as shown in FIG. 3), along the upstream-downstream axis ofthe filter, from the farthest downstream point of the filter (which inthe depiction of FIG. 3, will be provided by the point designed 145), tothe farthest upstream point of the filter (which in the depiction ofFIG. 3 will be the upstream face of upstream flange 130). (In these andin many cases, the overall thickness of a framed filter may beessentially equal to the overall thickness of the frame.) For purposesof such calculations, for two nested filters the nesting spacing is thedistance (along the same axis used for the filter thickness) from aparticular reference point on one filter, to the corresponding referencepoint on the other filter. In various embodiments, framed air filters asdisclosed herein may comprise a nesting factor that is less than about80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, or 35%. In furtherembodiments, framed air filters as disclosed herein may comprise anesting factor that is at least about 10, 20, or 30%.

By way of a representative example, portions of three exemplary nestedframed air filters 1, 1′ and 1″ are shown in FIG. 4 (in cross-sectionalslice view). The filter thickness “t” (which is the same for all threefilters) is designated, as is the nesting spacing S_(n) (with theupstream surfaces of the upstream flanges of the lowermost two filtersused as (randomly selected) reference points). In FIG. 4, the nestingfactor is approximately 55%.

It is noted that for a particular filter design, a nesting factor asdefined herein will be a constant that is set by the design. However, itwill be appreciated that the amount of space that can be saved inpacking the framed filters will increase with the number of filters thatare nested together. By way of a specific representative example,nestable framed air filters might each have a thickness of 20 mm andmight have a nesting factor of e.g. 70%, so that any two such filters,when nested together, comprise a thickness “overlap” of 6 mm. Thus,instead of two such filters adding to a total thickness of 40 mm, theywould add to a total nested thickness of 34 mm and would provide a space(thickness) savings of (40-34)/40 or 15%. Three such filters would addto a total nested thickness of 48 mm and would provide a space savingsof (60-48)/60 or 20%; five such filters would add to a total nestedthickness of 76 mm and would provide a space savings of (100−76)/100 or24%, and so on. It will thus be appreciated that nesting filters asdisclosed herein can provide significant savings in packaging, shipping,and storage costs, and it will be further appreciated that the greaterthe number of filters that are nested together the greater the savingscan be.

Further details of nestable filters are disclosed in U.S. patentapplication Ser. No. 13/968,609, filed evendate herewith, entitledNESTABLE FRAMED PLEATED AIR FILTER AND METHOD OF MAKING, which isincorporated by reference herein in its entirety.

FIGS. 3 and 4 illustrate another feature that may be useful in at leastsome embodiments. Pleated filter media 10 may comprise a pleating planeP_(p), which is defined as the plane of symmetry of the pleats, i.e. theplane that is halfway between the upstream and downstream pleat tips,measured along the upstream-downstream direction (as shown in FIG. 3).In at least some embodiments, the presence of filaments 40 will causethe pleating plane P_(p) of pleated media 10 to be offset downstreamfrom the aforementioned pinch plane P_(i) established by flanges 130 and160 of frame 12. That is, filaments 40 may lie largely in a stabilizingplane as mentioned earlier herein, which stabilizing plane may belargely coincident with pinch plane P_(p), thus causing pleated media 10to be displaced (offset) downstream from the pinch plane, i.e. towardthe open end of the framed filter. Such an offset is evidenced in FIG. 3by as the distance between planes P_(p) and P_(i).

Compressibility of Pleated Filter Media

FIG. 4 illustrates still another feature that may be useful in at leastsome embodiments. Specifically, in at least some embodiments pleatedfilter media 10 may be compressible, defined earlier herein as meaningthat the pleats of the filter medium can reversibly compress in anupstream-downstream direction e.g. when the framed air filter is nestedwith other framed air filters of like size and shape, and that thepleats can spring back to their original pleated configuration e.g. whenremoved from the nested configuration. As illustrated in FIG. 4, suchcompressibility allows that (if needed) the pleats of at least some ofthe nested filters (e.g., filters 1′ and 1″ as depicted in FIG. 4) cantemporarily deform (e.g., upon being nested). That is, in theillustrated embodiment of FIG. 4, a downstream portion of downstreampleats 30″ of filter media 10″ of filter 1″, upon being pressed againstfilaments 40′ of filter 1′ in the act of nesting these two filterstogether, can deform so as to allow the nesting to be performed.Downstream pleats 30′ of filter 1′ can likewise deform when pressedagainst filaments 40 of filter 1. In various embodiments, sufficientcompressibility of the pleated media 10 can provided so that nesting offilters can be achieved even when the nesting spacing is only 90, 80,70, or 60% of the pleat height (i.e., of the “nominal” pleat height inthe absence of any compressive force).

It is noted that even if pleated media 10 is compressible, it may not benecessary that any compression of any or all pleats thereof actuallyoccurs during a nesting process (if nesting is performed), depending onthe specific design of the filter (e.g., the filter thickness, pleatheight, and so on). It is further noted that although not shown e.g. inFIG. 4, upon nesting of filters together, some slight deformation offilaments 40 (e.g., away from a collectively purely planarconfiguration) may occur e.g. in addition to any of the above-describedcompression of pleated filter media 10 that may occur. Also, bydefinition a compressible pleated filter medium cannot have areinforcing layer of permanently deformable material (e.g., metal)pleated along therewith and continuously bonded to it. By permanentlydeformable material is meant a material (such as perforated metal layer,metal wire mesh, expanded metal, etc.) that, upon being pleated, tendsto remain in the pleated configuration (and thus to hold the pleatedmedia to which it is bonded in that same configuration so that it is nolonger compressible). An example of such a permanently deformable metallayer (an open wire mesh) is described in Example 1 of U.S. Pat. No.8,162,153 to Fox. This can be contrasted to materials (such as e.g.plastic netting, non-woven scrims, pre-filter layers and the like) that,even after being pleated (e.g. along with the filter media), do notresist deformation to a sufficient extent to render the pleated medianon-compressible.

Absence of Downstream Support

Beyond the requirement that a compressible pleated filter medium cannothave a reinforcing layer of permanently deformable material (e.g.,metal) pleated along therewith and continuously bonded to it, a framedpleated filter media as disclosed herein will not comprise any supportmember on the downstream face of the pleated air filter media. The termsupport member is used broadly in this context, and signifies any singlemember, or group of members, that provide downstream support. Such asupport member or members include, but are not limited to: one or morestrips of paperboard, plastic or metal; any perforated sheetlike layer(such as e.g. a perforated layer of paperboard, plastic, or metal); andany collection of filaments (such as e.g. a wire mesh, a scrim ofpolymeric materials, a scrim or mesh of inorganic materials such asfiberglass, a netting of polymeric material, a collection of bridgingfilaments as described herein, an expanded-metal mesh, a woven-wirematerial, and so on). Any such support member or members are prohibitedon the downstream face of pleated media 10, whether or not the member ormembers are attached to any portion of the downstream face (e.g., thedownstream pleat tips), and whether or not the member or members areattached to any portion of the support frame.

In short, the only item(s) of support that are allowed on the downstreamface of the framed pleated air filter are the downstream flanges 160 ofthe frame itself. In fact, any portion that extends (e.g. integrallyextends) from a downstream flange 160 of a major portion of frame 12,inwardly to a location that is more than 50% of the distance from theoutwardmost edge of that portion of the framed filter toward thegeometric center of the framed filter, is considered to be a supportmember and is not permitted.

The ordinary artisan will appreciate the surprising nature of theherein-presented disclosures that a framed pleated filter can be made,e.g. in sizes as large as e.g. 41×64 cm, that can survive the pressurestypically encountered in a residential HVAC system, without downstreamsupport of any kind (excepting the edge support provided by the supportframe), without the pleated media having any reinforcing layer ofpermanently deformable material (e.g., metal) pleated along therewith,and even (in some embodiments) with the pleated media having asinusoidal pleat pattern rather than being arranged in “zig-zag” stylepleats that effectively form triangular trusses that substantiallyincrease the stiffness of the pleated media.

Framed air filters as disclosed herein do not necessarily require pleatregistration between the different filters, although this may beoptionally done if desired. Thus in at least some embodiments, framedair filters as disclosed herein comprise pleat patterns that areunregistered, meaning that when the various individual framed, pleatedfilters are manufactured, the placement of the pleats of any one filtermedia (relative to its frame) is different from the placement of thepleats of at least one other filter media relative to that other filtermedia's frame. In other words, the pleats of any two framed pleatedfilters do not necessarily need to line up exactly when the two framedpleated filters are stacked (e.g., nested) together (even though thepleat spacings may often be similar or identical). Such an arrangementis shown in exemplary embodiment in FIG. 4, in which pleated filtermedia 10 of filter 1 is not registered with pleated filter media 10′ offilter 1′. It will be appreciated of course that even when no particularcare is taken to manufacture framed filters 1 with registered pleats,occasionally the pleat patterns of some framed filters may beapproximately or even closely registered with those of other framedfilters, due e.g. to random statistical fluctuations in themanufacturing process. And, in some embodiments, the manufacturingprocess may be controlled to provide that the pleats of multiple framedpleated filters are all registered with each other.

LIST OF EXEMPLARY EMBODIMENTS Embodiment 1

A framed pleated air filter, comprising: a non-self-supporting,compressible, pleated air filter media with an upstream face and adownstream face and a generally rectangular perimeter with four majoredges, wherein the non-self-supporting, compressible, pleated air filtermedia comprises a plurality of oppositely-facing pleats with a pleatdirection and with a plurality of upstream pleat tips and upstream pleatvalleys and downstream pleat tips and downstream pleat valleys, themedia further comprising a plurality of bridging filaments that are indiscontinuous contact with the upstream face of the media and that arebonded to at least some of the upstream pleat tips; and, a pinch framecomprising four major frame portions, with each major frame portionbeing mounted on one of the four major edges of the media, wherein theframed pleated air filter does not comprise any support member on thedownstream face of the pleated air filter media.

Embodiment 2

The filter of embodiment 1 wherein portions of the bridging filamentsare melt-bonded to at least some of the upstream pleat tips.

Embodiment 3

The filter of any of embodiments 1-2 wherein at least some of thebridging filaments are at least generally parallel to each other and areoriented at least generally perpendicular to the pleat direction.

Embodiment 4

The pleated filter of embodiment 3 wherein the bridging filamentscomprise a spacing between filaments of from around 3 mm to around 12mm.

Embodiment 5

The pleated filter of any of embodiments 1-4 wherein the bridgingfilaments are provided as part of a pre-existing scrim that isadhesively bonded to at least some of the upstream pleat tips.

Embodiment 6

The filter of any of embodiments 1-5 wherein the plurality ofoppositely-facing pleats of the media collectively define a pleatingplane, wherein upstream and downstream flanges of the four frameportions collectively define a pinch plane, and wherein the pleatingplane of the media is offset downstream from the pinch plane.

Embodiment 7

The filter of any of embodiments 1-6 wherein each major frame portioncomprises a sidewall angle of from about 100 degrees to about 160degrees and wherein the framed pleated air filter is nestable.

Embodiment 8

The filter of embodiment 7 wherein the non-self-supporting,compressible, pleated air filter media exhibits a pleat height andwherein the nestable framed pleated air filter exhibits a nestingspacing that is less than about 70% of the pleat height.

Embodiment 9

A kit comprising a plurality of framed pleated air filters of embodiment7 of like size and shape, wherein the framed pleated air filters arepackaged together so as to occupy a total thickness that is less thanabout 70% of the collective total of the thicknesses of the individualframed pleated air filters.

Embodiment 10

The kit of embodiment 9 wherein the pleated air filter media of at leastone of the framed pleated air filters of the kit comprises pleats thatare not registered with the pleated air filter media of at least oneother of the framed pleated filters of the kit.

Embodiment 11

The filter of any of embodiments 1-8 wherein the non-self-supporting,compressible, pleated air filter media comprises a nonwoven webcomprising organic polymeric fibers.

Embodiment 12

The filter of any of embodiments 1-8 and 11 wherein the pleats aresinusoidal pleats in which the upstream pleat tips and the downstreampleat tips exhibit an average radius of curvature of at least about 2 mmand in which none of the upstream pleat tips nor downstream pleat tipsare score-pleated.

Embodiment 13

The filter of any of embodiments 1-8 and 11-12 wherein the pleatfrequency is from about 0.3 to about 1.2 pleats per cm and wherein thepleat height is from about 4 to about 20 mm.

Embodiment 14

The filter any of embodiments 1-8 and 11-13 wherein the sidewall of eachframe portion comprises an outwardly angled inner sidewall and anoutwardly angled outer sidewall that meet at a downstream edge of theframe portion, and wherein the inner sidewall and the outer sidewall arepositioned at an angle relative to each other, of from about 10 to about40 degrees.

Embodiment 15

The filter of any of embodiments 1-8 and 11-14 wherein the air filtermedia comprises an electrostatically charged material.

Embodiment 16

A method of making a framed pleated air filter with an upstream face anda downstream face and a generally rectangular perimeter, the methodcomprising: providing a non-self-supporting, compressible, pleated airfilter media that comprises a plurality of oppositely-facing pleats witha pleat direction and with a plurality of upstream pleat tips andupstream pleat valleys and downstream pleat tips and downstream pleatvalleys; bonding a plurality of bridging filaments to at least some ofthe upstream pleat tips, so that the bonded bridging filaments are indiscontinuous contact with the upstream face of the pleated air filtermedia; and, mounting a pinch frame onto the generally rectangularperimeter of the filter media, wherein the framed pleated air filterdoes not comprise any support member on the downstream face of thepleated air filter media.

Embodiment 17

The method of embodiment 16 wherein the bridging filaments are extrudedas a molten extrudate and are contacted with the upstream pleat tipswhile still at least semi-molten.

-   Embodiment 18

The method of embodiment 16 wherein the bridging filaments are providedas part of a pre-existing scrim that is adhesively bonded to at leastsome of the upstream pleat tips.

EXAMPLES

Numerous Working Examples were made of a variety of designs andconfigurations. Air filter media were produced or obtained of a varietyof compositions, including unpleated media of the general type describedin U.S. Pat. No. 8,162,153 to Fox; unpleated media of the general typedescribed in U.S. Patent Application Publication 2008/0038976 toBerrigan; unpleated media obtained from Kimberly Clark (Irving, Tex.)under the trade designation 353H; and, unpleated media (of the generaltype described in U.S. Patent Application Publication 2004/0011204 toBoth) comprising a layer of electrostatically charged fibrillated fibers(30 g/m²) ultrasonically bonded to a 15 g/m² polymeric netting.

Samples of these media were corrugated (pleated) by being passed througha first nip comprising intermeshing gears of first and secondcorrugating rolls, in generally similar manner to the methods describede.g. in U.S. Pat. No. 5,256,231. The corrugation (pleating) patternranged from a pleat frequency of approximately 1.2 pleats per cm toapproximately 0.3 pleats per cm; the pleat height ranged fromapproximately 3 mm to approximately 19 mm. (The media were not scoredbefore, during or after the process of corrugating.) The resulting pleatpatterns were generally sinusoidal.

The pleated media was maintained in contact with the second corrugatingroll through a wrap angle to reach a second nip which was between thesecond corrugating roll and a smooth-faced backing roll. A strand diewas provided (of generally similar type to that described in U.S. Pat.No. 7,052,565 to Seth) through which multiple streams of moltenextrudate was extruded into the nip between the second corrugating rolland the backing roll, so as to provide bridging filaments that (afterthe molten extrudate had cooled and solidified) were melt-bonded to theupstream tips of the pleated media. Often, the bridging filaments andthe filter media comprised similar compositions (e.g. both comprisedpolypropylene), to enhance the melt-bonding. The bridging filaments wereoriented substantially perpendicular to the pleat direction (e.g., insimilar manner to that shown in FIG. 2); typical configurations providedbridging filaments at a spacing of approximately 1 strand per 0.64 cm offilter media width. In representative experiments, the strands wereroughly circular in cross section with a diameter of approximately0.4-0.5 mm.

In this manner numerous samples of non-self-supporting pleated airfilter media were produced, bearing bridging filaments (in this case,continuous bridging filaments) on one face thereof. The samples werethen framed with pinch frames in generally similar manner to thatdescribed in U.S. patent application Ser. No. 13/490,545, with thebridging filaments being present on what would become the upstream faceof the finished framed filter. The thus-formed framed filters (many ofwhich were of a nominal size of approximately 36 cm×64 cm×2.5 cm (14inches×25 inches×1 inch)) typically had a sidewall angle in the range ofapproximately 130 degrees. Many of these framed filters could be nested(as defined herein) with each other, with compression of the pleatsoccurring during nesting if necessitated by the pleat height in relationto the nesting spacing (in such cases, the media satisfactorily regainedits pleated configuration upon removing the filters from a nestedcondition). Framed filters were also made of nominal size ofapproximately 51 cm×64 cm×2.5 cm (20 inches×25 inches×1 inch), whichframed filters of this size were also found to be self-supporting.

Air filtration efficiency of various of these framed pleated filters wastested and was found to be generally satisfactory (e.g., similar tovarious control samples such as the same filtration media which had beene.g. pleated along with a support layer, e.g. wire mesh).

The property of a pleated filter media (in the absence of a supportframe) being self-supporting or not could be tested e.g. by placing apiece of the pleated filter media (that is, a pleat pack, without asupport frame having been mounted to the edges thereof), of a nominalsize of e.g. approximately 36 cm by 64 cm or 41 cm by 64 cm, into anopening of a frame tester e.g. of the general type described in U.S.Patent Application Publication 2012/0317944. Such a frame tester maycomprise an opening with flanges that support the perimeter edges of thepleated filter media to an overlap of approximately 1.3 cm (inwardlyfrom the edge of the media) on each perimeter edge. A pressuredifferential could then be applied to the pleated filter media (with thehigher pressure being applied to the upstream face of the filter), whichdifferential may be gradually stepped up to higher values. In suchtesting, prototypes of non-self-supporting pleated filter media of thegeneral type described herein (i.e., including upstream-side bridgingfilaments) would typically fail (e.g., would deform/bow in a downstreamdirection so as to become dislodged from the frame tester opening) at anapplied air pressure of no more than 0.05-0.07 kPA (i.e., 0.2-0.3 inchesof water). In fact, many of the pleated filter media samples describedabove could be easily discerned as being non-self-supporting evenwithout performing such a test (e.g., merely by inspection of how limpand floppy the pleated media was, even in the presence of bridgingfilaments, as would be readily apparent to the ordinary artisan). Theframed filters as made were found to be able to satisfactorily withstandthe air pressure of a typical residential HVAC system (as discussedherein).

It will be apparent to those skilled in the art that the specificexemplary structures, features, details, configurations, etc., that aredisclosed herein can be modified and/or combined in numerousembodiments. All such variations and combinations are contemplated bythe inventor as being within the bounds of the conceived invention.Thus, the scope of the present invention should not be limited to thespecific illustrative structures described herein, but rather by thestructures described by the language of the claims, and the equivalentsof those structures. To the extent that there is a conflict ordiscrepancy between this specification and the disclosure in anydocument incorporated by reference herein, this specification willcontrol.

What is claimed is:
 1. A framed pleated air filter, comprising: anon-self-supporting, compressible, pleated air filter media with anupstream face and a downstream face and a generally rectangularperimeter with four major edges, wherein the non-self-supporting,compressible, pleated air filter media comprises a plurality ofoppositely-facing pleats with a pleat direction and with a plurality ofupstream pleat tips and upstream pleat valleys and downstream pleat tipsand downstream pleat valleys, the media further comprising a pluralityof bridging filaments that are in discontinuous contact with theupstream face of the media and that are bonded to at least some of theupstream pleat tips; and, a pinch frame comprising four major frameportions, with each major frame portion being mounted on one of the fourmajor edges of the media, wherein the framed pleated air filter does notcomprise any support member on the downstream face of the pleated airfilter media, and wherein each major frame portion comprises a sidewallangle of from about 100 degrees to about 160 degrees and wherein theframed pleated air filter is nestable.
 2. The filter of claim 1 whereinportions of the bridging filaments are melt-bonded to at least some ofthe upstream pleat tips.
 3. The filter of claim 1 wherein at least someof the bridging filaments are at least generally parallel to each otherand are oriented at least generally perpendicular to the pleatdirection.
 4. The pleated filter of claim 3 wherein the bridgingfilaments comprise a spacing between filaments of from around 3 mm toaround 12 mm.
 5. The pleated filter of claim 1 wherein the bridgingfilaments are provided as part of a pre-existing scrim that isadhesively bonded to at least some of the upstream pleat tips.
 6. Thefilter of claim 1 wherein the plurality of oppositely-facing pleats ofthe media collectively define a pleating plane, wherein upstream anddownstream flanges of the four frame portions collectively define apinch plane, and wherein the pleating plane of the media is offsetdownstream from the pinch plane.
 7. The filter of claim 1 wherein thenon-self-supporting, compressible, pleated air filter media exhibits apleat height and wherein the nestable framed pleated air filter exhibitsa nesting spacing that is less than about 70% of the pleat height.
 8. Akit comprising a plurality of framed pleated air filters of claim 1 oflike size and shape, wherein the framed pleated air filters are packagedtogether so as to occupy a total thickness that is less than about 70%of the collective total of the thicknesses of the individual framedpleated air filters.
 9. The kit of claim 8 wherein the pleated airfilter media of at least one of the framed pleated air filters of thekit comprises pleats that are not registered with the pleated air filtermedia of at least one other of the framed pleated filters of the kit.10. The filter of claim 1 wherein the non-self-supporting, compressible,pleated air filter media comprises a nonwoven web comprising organicpolymeric fibers.
 11. The filter of claim 1 wherein the pleats aresinusoidal pleats in which the upstream pleat tips and the downstreampleat tips exhibit an average radius of curvature of at least about 2 mmand in which none of the upstream pleat tips nor downstream pleat tipsare score-pleated.
 12. The filter of claim 1 wherein the pleat frequencyis from about 0.3 to about 1.2 pleats per cm and wherein the pleatheight is from about 4 to about 20 mm.
 13. The filter of claim 1 whereinthe sidewall of each frame portion comprises an outwardly angled innersidewall and an outwardly angled outer sidewall that meet at adownstream edge of the frame portion, and wherein the inner sidewall andthe outer sidewall are positioned at an angle relative to each other, offrom about 10 to about 40 degrees.
 14. The filter of claim 1 wherein theair filter media comprises an electrostatically charged material.
 15. Amethod of making the framed pleated air filter of claim 1 with anupstream face and a downstream face and a generally rectangularperimeter, the method comprising: providing a non-self-supporting,compressible, pleated air filter media that comprises a plurality ofoppositely-facing pleats with a pleat direction and with a plurality ofupstream pleat tips and upstream pleat valleys and downstream pleat tipsand downstream pleat valleys; bonding a plurality of bridging filamentsto at least some of the upstream pleat tips, so that the bonded bridgingfilaments are in discontinuous contact with the upstream face of thepleated air filter media; and, mounting a pinch frame comprising fourmajor frame portions onto the generally rectangular perimeter of thefilter media, wherein the framed pleated air filter does not compriseany support member on the downstream face of the pleated air filtermedia, and wherein each major frame portion comprises a sidewall angleof from about 100 degrees to about 160 degrees and wherein the framedpleated air filter is nestable.
 16. The method of claim 15 wherein thebridging filaments are extruded as a molten extrudate and are contactedwith the upstream pleat tips while still at least semi-molten.
 17. Themethod of claim 15 wherein the bridging filaments are provided as partof a pre-existing scrim that is adhesively bonded to at least some ofthe upstream pleat tips.